ob-C.el: Add support for specifying namespaces in C/C++

* lisp/ob-C.el (org-babel-C-expand-C): Add a :namespaces export option
  to C++ org babel blocks. Namespaces specified here will be added to
  the file in the format 'using namespace %s;'. Multiple namespaces
  can be specified, separated by spaces.

TINYCHANGE

etc/ORG-NEWS

@@ -218,6 +218,20 @@ To use =vertica= in an sql =SRC_BLK= set the =:engine= like this:
   SELECT * FROM nodes;
   ,#+END_SRC
 #+END_EXAMPLE
+**** C++: New header ~:namespaces~
+
+The new ~:namespaces~ export option can be used to specify namespaces
+to be used within a C++ org source block.  Its usage is similar to
+~:includes~, in that it can accept multiple, space-separated
+namespaces to use.  This header is equivalent to adding ~using
+namespace <name>;~ in the source block. Here is a "Hello World" in C++
+using ~:namespaces~:
+
+#+begin_example
+  ,#+BEGIN_SRC C++ :results output :namespaces std :includes <iostream>
+    cout << "Hello World" << endl;
+  ,#+END_SRC
+#+end_example
 
 *** New ~function~ scope argument for the Clock Table
 Added a nullary function that returns a list of files as a possible

lisp/ob-C.el

@@ -46,6 +46,19 @@
 
 (defvar org-babel-default-header-args:C '())
 
+(defconst org-babel-header-args:C '((includes . :any)
+				    (defines . :any)
+				    (main    . :any)
+				    (flags   . :any)
+				    (cmdline . :any)
+				    (libs    . :any))
+  "C/C++-specific header arguments.")
+
+(defconst org-babel-header-args:C++
+  (append '((namespaces . :any))
+	  org-babel-header-args:C)
+  "C++-specific header arguments.")
+
 (defcustom org-babel-C-compiler "gcc"
   "Command used to compile a C source code file into an executable.
 May be either a command in the path, like gcc
@@ -196,15 +209,18 @@ its header arguments."
 	(colnames (cdr (assq :colname-names params)))
 	(main-p (not (string= (cdr (assq :main params)) "no")))
 	(includes (org-babel-read
-		   (or (cdr (assq :includes params))
-		       (org-entry-get nil "includes" t))
+		   (cdr (assq :includes params))
 		   nil))
 	(defines (org-babel-read
-		  (or (cdr (assq :defines params))
-		      (org-entry-get nil "defines" t))
-		  nil)))
+		  (cdr (assq :defines params))
+		  nil))
+	(namespaces (org-babel-read
+		     (cdr (assq :namespaces params))
+		     nil)))
     (when (stringp includes)
       (setq includes (split-string includes)))
+    (when (stringp namespaces)
+      (setq namespaces (split-string namespaces)))
     (when (stringp defines)
       (let ((y nil)
 	    (result (list t)))
@@ -224,6 +240,11 @@ its header arguments."
 		(mapconcat
 		 (lambda (inc) (format "#define %s" inc))
 		 (if (listp defines) defines (list defines)) "\n")
+		;; namespaces
+		(mapconcat
+		 (lambda (inc) (format "using namespace %s;" inc))
+		 namespaces
+		 "\n")
 		;; variables
 		(mapconcat 'org-babel-C-var-to-C vars "\n")
 		;; table sizes